Field of the Invention
The present invention relates in general to charge pumps, and more particularly to a self-regulating, current in, current out (current to current) charge pump.
Description of the Related Art
Conventional charge pumps typically convert one voltage to another voltage. Many configurations operate as doublers or triplers or the like in which the output voltage is a selected multiple of the input voltage. In many applications it is desired to provide a current in, current out (or current to current) charge pump, that is, a charge pump that converts an input current to an output current. One such application is an analog comparator, in which it is desired to provide the tail current (or common source current) for PMOS transistors connected as a differential pair at the input of the analog comparator. It is beneficial to have the output current track the input current over process and temperature variations so that the ratio of the output current to the input current remains approximately constant. A conventional approach is to provide regulation circuitry with feedback to maintain the desired current conversion ratio between the input and output of the charge pump. It has been determined, however, that such regulation circuitry can lead to instabilities caused by the feedback regulation circuitry.